Accelerator（accelerator）The charged particles are artificially accelerated to higher energydevice。This device can generate various energiesElectronics、proton、Deuteron、Alpha particleAnd some other weightsIons。Using these directly accelerated charged particles to interact with matter can also produce a variety of charged and uncharged secondary particles, such asGamma particle、neutronAnd variousmeson, hyperonAntiparticleEtc.Most accelerators in the world today have an energy of 100 trillionElectron voltThe following low-energy accelerators are mostly used in other fields, such as chemistryRadiobiologyBasic research in radiation medicine, solid state physics, industrial photography, disease diagnosis and treatment, activation analysis of high-purity substances, radiation treatment of some industrial products, radiation treatment of agricultural products and other foods, simulationCosmic radiationAnd simulated nuclear explosion.Over the years, various types ofIon implanter。For the semiconductor industryimpurityThe old process of doping instead of thermal diffusion.The yield and performance indexes of semiconductor devices have been greatly improved.Many new devices that can not be realized by the old process are coming out constantly, and the integration of integrated circuits is thus greatly improved.
Accelerator classification
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Charged particles will be accelerated by the electromagnetic force in the electric field to increase energy.Electric field can exist in three different forms: electrostatic field, magnetic induction field and alternating electromagnetic field. Accelerator is developed by the principle of accelerating charged particles with these three kinds of electric fields.Since the 1930s, after more than 70 years of development, there have been many types of accelerators, and their classification standards are also many. For example, according to the types of accelerating particles, they can be divided into electron accelerators, protons andHeavy ion acceleratorAnd micro particle (powder, dust, etc.) accelerator (also called particle cluster accelerator);According to the energy of accelerating particles, it can be divided into low-energy accelerator (with energy below 100MeV), medium energy accelerator (with energy between 100MeV and 1GeV) and high-energy accelerator (with energy between 1 and 100GeV). The accelerator with energy above 100 GeV is called super high-energy accelerator;According to beam intensity, it can be divided into high current accelerator (beam intensity above 1mA), medium current accelerator (beam intensity above 10 μ A~1mA) and low current accelerator (beam intensity below 10 μ A);According to the type of accelerating electric field, it can be divided into high-voltage accelerator, electromagnetic induction accelerator and high-frequency resonant accelerator;According to the shape of particle motion orbit, it can be divided intolinear acceleratorAnd circular (or annular) accelerators.Linear accelerator includes DC high-voltage accelerator and RF collider.Circular accelerator includescyclotron, phase stabilized accelerator, electron induction accelerator,synchrotron, weak focus synchrotron, strong focus synchrotron andAnnular colliderEtc.[1]
Basic composition
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Accelerator is a complex equipment, which is generally composed of the following four basic parts:
(1) Particle source
Such as electron gun, ion source, etc., to provide charged particle beam that needs to be accelerated.
(2) Vacuum acceleration structure
For example, the accelerator tube, RF accelerator chamber and annular accelerator chamber generate a certain acceleration electric field in vacuum to accelerate particles.
(3) Guidance focusing system
The accelerated particle beam is guided and constrained by a certain electromagnetic field to accelerate along a certain orbit, such as the dominant magnetic field of the annular accelerator.
(4) Beam transport and analysis system
A system consisting of electrons, magnetic field lenses, bent magnets, and electric and magnetic field analyzers is used to transport and analyze charged particle beams between particle sources and accelerators.
In addition, there are auxiliary systems such as beam monitoring device, electromagnetic stability control device, vacuum device, electrical equipment operating equipment, etc.[1]
The early exploration of accelerator can be traced back to the 1920s.As early as 1919, British scientistsrutherford(E. Rutherford) The energy in the natural radioactive source is several MeV, and the speed is
The high speed alpha particle beam (i.e. helium core) of m/s is used as the "shell" to bombard the "target" of metal foil with a thickness of only 0.0004cm, realizing the first artificial in the history of human sciencenuclear reaction。Using the zinc sulfide fluorescent screen placed behind the target, the distribution of particle scattering was measured, and it was found that the atomic nucleus itself had a structure, which inspired people to seek higher energy particles as "shells".
On the basis of the early research of accelerators, relevant scientists around the world have been committed to the research and development of higher energyParticle accelerator。
Kircroft
In 1932, American scientist J.D. Cockcroft and Irish scientist E.T.S. Walton built the first DC accelerator in the world - named as Cockcroft Walton DCHigh pressure acceleratorA proton beam with energy of 0.4MeV was used to bombard the lithium target to obtain the nuclear reaction experiment of alpha particles and helium.This is the first time in history that a nuclear reaction is realized by artificially accelerating particles, so the 1951Nobel Prize in Physics。
Van de Graaff
accelerator
In 1933, R.J. van de Graaff, an American scientist, invented a high-voltage accelerator using another method to generate high voltage, which was named Van de Graaff electrostatic accelerator.The above two particle accelerators are DC high-voltage type, and their energy for accelerating particles is limited by high-voltage breakdown, about 10MeV.
Lawrence and cyclotron
In 1924, G. Ising, and in 1928, E. Wideroe, respectively, invented linear accelerators based on the principle of adding high-frequency voltage to drift tubes. Due to the limitation of high-frequency technology at that time, such accelerators can only accelerate potassium ions to 50keV, which is of little practical significance.But inspired by this principle,U.S.Aexperimental physicist Lawrence(E.O. Lawrence) built the cyclotron in 1932 and used it to generate artificialradio isotopeHe won the Nobel Prize for Physics in 1939.This is the first person to win this honor in the history of accelerator development.
Due to the restriction between the mass and energy of the accelerated particle, the cyclotron can only accelerate the proton to about 25MeV. The reason is that the relationship between the acceleration and the external force is no longer applicable with the constant increase of the particle speedNewton's law of motionThat is, the frequency of the high-frequency accelerating electric field and the cyclotron frequency no longer match;If acceleratormagnetic fieldThe intensity of is designed to increase synchronously with the particle energy along the radius direction, which can accelerate the proton to hundreds of MeV, calledIsochronous cyclotron。
Former Soviet scientist Viktor Lier
In order to further explore the structure of the atomic nucleus and generate newElementary particleWe must study the principle of building particle accelerators with higher energy.In 1945,Former Soviet UnionScientists V.I. Veksler and American scientistsMacmillan(E.M. McMillan) independently discovered the principle of automatic phase stabilization, and M.L. Oliphant, a British scientist, also proposed to build an accelerator based on this principle - phase stabilization accelerator.
American scientist Macmillan
The discovery of the principle of automatic phase stabilization is a major revolution in the history of accelerator development, which has led to a series of new accelerators that can break the energy limit of cyclotron:Synchronous cyclotron(The frequency of high-frequency accelerating electric field decreases with the increase of the energy of double accelerating particles, keeping the cyclotron frequency of particles synchronized with the accelerating electric field), modern proton linear accelerator, synchrotron (usingmagnetic field intensityThe ring magnet increased with the increase of particle energy to maintain the circular track of particle motion, but maintain the high-frequency frequency of the acceleration field unchanged).
Since then, the construction of the accelerator has solved the limitation in principle, but the improvement of energy has been limited economically.With the increase of energy, the weight and cost of magnets used in cyclotron and synchronous cyclotron rise sharply, and the increase of energy is actually limited to below 1GeV.Although the cost of the ring magnet of the synchrotron has been greatly reduced, the vacuum box must be very large due to the poor horizontal focusing force, resulting in large pole gap of the magnet, which still requires a very heavy magnet. It is still unrealistic to use it to accelerate the proton to more than 10GeV.
In 1952, American scientists E.D. Courant, M.S. Livingston and H.S. Schneider published a paper on the strong focusing principle. Building a strong focusing accelerator based on this principle can greatly reduce the size of the vacuum box and the cost of magnets, making it possible for the accelerator to develop to higher energy.This is another revolution in the history of accelerator development, with great influence.Since then, the strong focusing principle has been widely used in annular or linear accelerators.
Lawrence National Laboratory built a 6.2GeV energy weak focusing proton synchrotron in 1954, with a total weight of 10000 tons of magnets.andBrookhaven National LaboratoryThe strong focused proton synchrotron with 33GeV energy has a total magnet weight of only 4000 tons.This shows the great practical significance of the strong focusing principle.
American scientist Kurt
In 1940, American scientist D.W. Kerst developed the firstInduction accelerator。However, due to the energy loss caused by the electromagnetic radiation continuously emitted in the tangent direction when the electron moves along the curve, the energy increase of the electron induction accelerator is limited, and the limit is about 100 MeV.Electron synchrotronThe use of electromagnetic fields to provide acceleration energy can allow greater radiation loss, with a limit of about 10GeV.There is no radiation loss when the electron moves in a straight line, and it is accelerated by electromagnetic fieldElectron linear acceleratorThe electron can be accelerated to 50GeV, which is not the limit of theory, but the limit of high cost.
The development of accelerator energy to such a level exposes new problems from the perspective of experiment.Use accelerator toHigh-energy physicsExperiments generally use accelerated particles to bombard the nucleons in the stationary target, and then study the momentum, direction, charge, quantity, etc. of the generated secondary particles. The actual useful energy of accelerated particles to participate in high-energy reactions is limited.If two beams of accelerating particles collide, the accelerated particle energy can be fully used for high-energy reactions or the generation of new particles.
Italian scientist Tauschek
In 1960, Italian scientist B. Touschek put forward this principle for the first time, and built an AdA collider with a diameter of about 1 meter in Italy's Frascati National Laboratory, which verified the principle and ushered in a new era of accelerator development.
Modern high-energy accelerators are basically in the form of colliders, which have been able to increase the equivalent energy of high-energy reactions from 1 TeV to 10~1000 TeV, which is another fundamental leap in the history of accelerator energy development.
Particle accelerator
A device that produces high-speed charged particles by manual means.It is an important tool for exploring the properties, internal structures and interactions of atomic nuclei and particles, and has important and extensive practical applications in industrial and agricultural production, medical care, science and technology, etc.
rutherford
Since ErutherfordNatural in 1919radioactive elementEmitted aradialbombardmentnitrogenAtoms first realizedelementAfter the artificial transformation ofHigh-speed particleTo transform the atomic nucleus.Natural radioactivityThe particle energy provided is limited, only a few megaelectron volts (MeV). Although the energy of particles in natural cosmic rays is very high, the particle flow is extremely weak, for example, the energy is 10fourteenElectron voltOnly one particle of (eV) falls on an area of 1 square meter every hour, and it is uncontrollablecosmic raysIt is difficult to carry out research work because of the type, quantity and energy of particles in.Therefore, in order to carry out experimental research with expected goals, people have developed and built a variety of particle accelerators over the decades, and their performance has been continuously improved.Most of the newTransuranic elementAnd thousands of new synthetic radioactivitynuclideAnd systematically and deeply studyNucleusThe basic structure ofNuclear physicsRapid development and maturity;The development of high-energy accelerators has led people to discover thatbaryon、meson、LeptonAnd variousResonance stateHundreds of particles, including particlesParticle physics。Over the past 20 years, the application of accelerators has gone far beyond the fields of nuclear physics and particle physics, such asmaterial science 、Surface physics, molecular biology, photochemistry and other scientific and technological fields have important applications.Accelerators are widely used in isotope production, tumor diagnosis and treatmentRadiation disinfectionNDT, polymer irradiation polymerization, material irradiation modificationion implantation , ion beam microanalysis andSpace radiationSimulationnuclear explosionSimulation, etc.So far, thousands of particle accelerators have been built around the world, a small part of which is used for basic research in atomic nucleus and particle physics. They continue to develop in the direction of improving energy and beam quality;Most of the rest are "small" accelerators that mainly use particle ray technology.
The structure of particle accelerator generally includes three main parts: ①Particle source, particles used to provide the required acceleration, includingElectronics、positron、proton、Antiprotonas well asHeavy ionWait a minute. ②vacuumAcceleration system, in which there is a certain form of accelerationelectric fieldIn order to accelerate the particles without being scattered by air molecules, the whole system is placed invacuum degreeVery high vacuum chamber. ③The guidance and focusing system uses a certain form of electromagnetic field to guide and constrain theaccelerateOfParticle beam, make it follow the presettrackAccept the acceleration of electric field.All these require the integration and cooperation of high, precise and sophisticated technologies.
AcceleratorefficiencyThe index is the energy that particles can reach and the intensity of particle flow（Current intensity）。According to the size of particle energy, accelerators can be divided intoLow-energy accelerator(energy less than 10eighteV）、Intermediate energy accelerator(energy at 10eight～10nineeV）、High energy accelerator(energy at 10nine～10twelveEV) and ultra-high energy accelerator (energy at 10twelveAbove eV).At present, low-energy and intermediate energy accelerators are mainly used for various practical applications.
Three revolutions
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In 1945, former Soviet scientist Viktor Lier and American scientist Macmillan independently discovered the principle of automatic phase stabilization.In 1946, the first phase stabilized accelerator was built in Berkeley, the United States. Since then, a series of synchronous accelerators have been born, including the synchronous cyclotron.This is the first revolution in accelerator development.In 1952, American scientists Cologne, Livingston and Snyder proposed the strong focusing principle, which was then widely used in ring accelerators and linear accelerators.This is the second revolution of accelerator development.In 1960, Tauschek first proposed the concept of collider, that is, two particles were injected into the synchrotron in the opposite direction and collided at the designated location. Under his leadership, a collider with a diameter of 1m, named AdA, was built in Frascati, Italy, opening a new era of accelerator development.This is the third revolution of accelerator development.[1]
Collider
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Fig. 1 Accelerator
Since the first accelerator was built in the world, the energy of the accelerator has increased by about 9 orders of magnitude in more than 70 years (see Figure 1), and the cost per unit of energy has decreased by about 4 orders of magnitude. Such an amazing development speed is rare in all scientific fields.
With the continuous improvement of accelerator energy, human understanding of the microscopic material world has gradually deepened, and the research of particle physics has made great achievements.A device that artificially accelerates charged particles to achieve very high speed. Accelerators use a certain form of electromagnetic field to accelerate charged particles such as electrons, protons, or heavy ions, so that they can have high-speed charged particle beams with the speed of thousands, tens of thousands, or even near light. It is an important tool for people to recognize atomic nuclei, explore basic particles, and study the deep structure of matter,At the same time, with the continuous development of accelerator technology, various new technologies and new principles are constantly updated and broken through, further promoting the advancement of new technologies. The research and development of accelerator also bring important and extensive applications in industrial and agricultural production, medical care, national defense construction and other aspects
As early as the 1920s, scientists discussed many schemes for accelerating charged particles and carried out many experiments. Among them, E. Videro was the first to propose the acceleration principle. In the early 1930s, high-voltage multipliers, electrostatic accelerators and cyclotrons were introduced one after another, and the researchers obtainedThe nobel prize in physicsSince then, with the deepening of people's research on the deep structure of the microscopic material world, the demand for various fast particle beams in various scientific and technological fields has been growing, a variety of new acceleration principles and methods have been proposed, and accelerators with various characteristics have been developed, including electron induction accelerator, linear accelerator, strong focus high-energy acceleratorSector focused cyclotronIn 1956, Kester proposed to passHigh-energy particleThe concept of beam to beam collision to improve the effective interaction energy has led to the development of high-energy colliders
Over the past decades, people have discovered most of the new transuranic elements and synthesized thousands of newArtificial radionuclideAnd conducted systematic and in-depth research on the basic structure of atomic nuclei and their changing laws, which promoted the development and maturity of nuclear physics, and established a new discipline of particle physics. In the past 20 years, the development and application of accelerators have made materials scienceSurface physicsMolecular biology and photochemistry have made important progress
The development of accelerators in China began in the late 1950s, with the development and production of high-voltage multipliers, electrostatic accelerators, electron induction accelerators, electron and proton linear accelerators, and cyclotrons. In recent years, more advanced accelerators have made significant progress in China,BeijingCompletedElectron positron colliderThe development and application of Chinese accelerators have entered the world's advanced ranks
China
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1955
Fig. 2 Accelerator
The Institute of Atomic Energy of the Chinese Academy of Sciences has built a 700eV proton electrostatic accelerator.Around 1957
Tsinghua UniversityThe 400keV proton pressure doubling accelerator was completed.
1958~1959
The 2.5Mev electron cyclotron of Tsinghua University emits beams.
1964
The 30 MeV electron linear accelerator of Institute of High Energy, Chinese Academy of Sciences was completed.
1982
China's first self-designed and manufacturedProton linacThe proton beam with energy of 10MeV is introduced for the first time,pulseThe flow reaches 14mA
LanzhouThe separation sector cyclotron (HIRFL) used by the Institute of Modern Physics for accelerator heavy ions was built.
1989
Beijing SpectrometerPush it to the collision point, start the overall inspection, and use the obtained Baba case for calibration.Beijing Spectrometer began its physical work.
Significant progress has been made in the installation and commissioning of the first phase of the Beijing Electron Positron Collider Major Reconstruction Project (BEPC II).At 16:41 on November 19 of the same year, the electron beam current intensity displayed on the oscilloscope in the linear accelerator control room was more than 2A, marking an important phased achievement in the improvement of BEPC Ⅱ linear accelerator.
2005
Beijing Electron Positron Collider (BEPC) officially ended operation.The second phase of the Beijing Electron Positron Collider Major Reconstruction Project (BEPC II) with an investment of 640 million yuan - the reconstruction of the new double ring electron positron collider storage ring officially began.The performance of the new Beijing Electron Positron Collider will be 3 to 7 times that of the same type of device in the United States, which is of great significance for basic scientific research such as the study of quark particles whose volume is one billionth of the atomic nucleus.
Reaction mode
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Figure 3 Accelerator Integration Unit
The research on the structure of matter under the condition of high-energy accelerator is essentially about the relative change (transformation) relationship in quantity of energy states between natural energy clusters (or energy clusters, energetic particles) in natural state.From the perspective of arc theory, under the condition of bombarding arc like sub structure (atom) with high-energy accelerator and other methods, we can getWeak interactionRelationship: 1. Symmetry theory (general symmetry theory) 2. Asymmetry theory, obtained under special conditions.If we bombard energetic particles (arcons, subatomic structures), we get strong interaction relations: asymptotic free theory, etc.
Why?
Both of the above actions occur at the level of energy state rather than the level of material state;The relationship between generic energy clusters and energy clusters.
Weak interaction: when any external energy group bombards the arclike sub structure, when it enters the arclike sub structure along the time axis (from energy to energy), the external energy will enter the arclike sub result body when it enters the arclike sub result body, and then arc cooperation will occur to produce a symmetric arc, which shows that two energy groups with opposite rotation directions and equal mass are released externally, that is, symmetric arc reaction.EnergizedEnergy levelIt is limited to the energy (assumed equal to 1) of the time axis of the bombarded arcon: when it is less than 0 and greater than 1, it cannot produce pairs of energy particles.Only when<1,>0, can sub particles be generated;At this level, many sub particles can be generated, which is theoretically unlimited.
Asymmetric weak interaction: if the external energy and the spatial axis of the arclike sub enter the system horizontally, due to the asymmetry of the time axis on the spatial axis (1/3), all weak interactions occur in the energy exchange process of the arclike sub structure, which is essentially an artificial disturbance to the natural energy state, not a structural change of matter.Arc like substructure is a kind of universal rigid structure in the process of energy state transformation.When the external energy enters, these external energy will be "trained" to form appropriate secondary particles and be released.These processes can be repeated.The only structure of all natural energy states when their energy is transformed into each other, that is, arclike sub bodies.The weak interaction is actually the physical observation result of the interference of arclike bodies under artificial conditions.The natural energy state is like a calm lake, and the artificial force has created several ripples;When these artificial disturbances stop, the natural energy state will return to its original state without any change.The theories or laws that people have summarized are only the observation results of those few ripples.We still know nothing about the natural energy state or physical structure.
The different strong interactions all take place at the energy sub level (state) of the energy state.The unified structure of energy sub states, namely, absolute arcons.Its space-time axis is absolutely identical, and the smallest energy sub unit that constitutes the absolute arcon is calledhadron。The strong interaction is to study the relationship between the energy units of absolute arcons.Here, the artificial energy is required to have a very high energy level state, and this interaction can only be excited when using very high energy.The strong interaction does not show any new particle generation or sub particle pair generation;In other words, if produced, it is the transformation form of collision energy.How to transform depends only on the amount of artificial external energy absorbed by the absolute arcon.Normally, it does not occur.Most of them are released in the form of photons, with extremely short life.
An absolute arc is like a pitted ball. Its pitted point corresponds to the smallest energy unit. When there is no external energy, the "position" of each pitted point is the same, that is, free, and the existence of the same pitted point can be "seen" from any direction.When an external force (external energy) is applied to it, the spherical surface will collapse. At this time, symmetrical pits on the collapse edge will move symmetrically away from each other, as if separated.Because of the stability of the absolute arc itself, that is, its rejection of artificial energy, it seems that two pits are desperately trying to restore the original state. The greater the force, the greater the depression, and the stronger the resilience;The smaller the depression, the weaker the resilience. According to the view of modern physics, it is asymptotically free.These are false appearances.
In summary, weak interactions and their laws as well as strong interactions and their laws, such asYang ZhenningAnd David # 26684;Ross, David#27874；Li CeheFrank#32500；Both the strong interaction theory and the asymptotic freedom theory of Ercek and others are based on the physical cognition theory that describes the phenomenon of the natural state when it is disturbed, rather than the physical theory of the natural state.The fundamental mistake lies in that the natural epistemology is wrong, and only the arc theory can correctly summarize and elaborate the various natural intrinsic state structures.
application
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The application of low-energy accelerators is an important branch of the nuclear technology application field. At present, most of the thousands of accelerators operating around the world are low-energy accelerators widely used in industries, agriculture, medical and health care and other fields.The application of low-energy accelerator in these fields has greatly changed the appearance of these fields and created huge economic and social benefits.
Industry
1) Irradiation processing
Irradiation processing with electron beam or X-ray generated by accelerator has become an important means and process in chemical, power, food, environmental protection and other industries. It is a new processing technology.It is widely used in polymer crosslinking modification, coating curing, polyethylene foaming, heat shrinkable materials, semiconductor modification, wood plastic composite preparation, food sterilization and preservation, flue gas irradiation desulfurization and denitrification and other processing processes.
The irradiated products have many excellent characteristics. For example, after 105Gy irradiation, the electrical and thermal properties of polyethylene cables have been greatly improved. The operating temperature before irradiation is 60~70 ℃, and the long-term operating temperature after irradiation can reach more than 120 ℃.At present, China has more than 40 production lines for irradiation processing with accelerators.
2) NDT
Non destructive testing is to detect the internal conditions of materials, products or components without damaging them, and to judge whether there are internal defects.There are many modern NDT methods, such as:Ultrasonic flaw detection methodEddy current flaw detection, fluorescent flaw detection andRadiographic testingLaw, etc.Radiographic testing can be used to check both the surface and the internal defects of the workpiece.The equipment can use gamma rays produced by radioisotope Co-60, low-energy X-ray produced by X-ray machine and high-energy X-ray produced by electron accelerator.Especially, the flaw detection accelerator has high penetration ability and sensitivity. As a final inspection method or a verification method of other flaw detection methods, and in quality control, it is widely used in defect inspection of large castings, forged weldments, large pressure vessels, reactor pressure shells, rocket solid fuel and other workpieces.This flaw detection accelerator is mainly based on the electron linear accelerator.
Radiographic testing methods can be divided into three types according to the different methods of receiving and processing the radiation of the workpiece:
This method is similar to taking X-ray during our physical examinationfilmSimilarly, the ray receiver is X-ray film.During flaw detection, the film box with X-ray film shall be close to the back of the workpiece to be inspected. After the workpiece is irradiated with X-ray, the film will be sensitized through the radiation of the workpiece. At the same time, the actual situation inside the workpiece will be reflected on the emulsion of the film. After the photosensitive film is processed, the defect of the workpiece and the type, position, shape and size of the defect can be clearly understood.
b、Radiography
The ray receiver of this method is an array detector or a fluorescent intensifying screen.The former is Tsinghua University andTsinghua TongfangLarge container inspection series products jointly developed and produced.The latter is the X-ray security inspection system for baggage and parcels in airports and railways, and can also be used for industrial NDT.This method, together with the image processing system, can display the real situation of the inside of the object online in real time.
Similar to the principle of medical CT, CT technology iscomputerAssisted tomography.CT technology using accelerator as X-ray source is an advanced nondestructive testing method, mainly for largeSolid rocket motorAnd the detection of precision workpiece.itsDensity resolutionIt can reach 0.1%, one order of magnitude higher than conventional ray technology.It has important application value in defect detection, dimension measurement, assembly structure analysis of precision workpiece in aerospace, aviation, weapons, automobile manufacturing and other fields.
3) Ion implantation
Good physical, chemical and electrical properties can be obtained by implanting ions of certain energy into the surface of solid materials with accelerator.Modification of semiconductor devices, metal materials andlarge-scale integrated circuitProduction has been appliedIon implantation technology。China now has more than 100 ion implantation machines of various types.Among them, China has produced more than 140 ion implanter with energy of 150KeV~600KeV (1KeV=1 × 10threeeV），The current intensity is 0.5mA to more than 10 mA.
Agriculture
The application of accelerators as nuclear technology application equipment in agriculture, which have been widely used in some countries, has obvious economic benefits in three aspects:
1) Irradiation breeding
The application of accelerators in irradiation breeding is mainly to use the high-energy electrons, X-rays, fast neutrons or protons generated by accelerators to irradiate seeds, buds, embryos or grain pollen of crops, so as to change the genetic characteristics of crops and make them develop in the direction of optimization.It has played a significant role in increasing yield, improving quality, shortening growth period and enhancing stress resistance by radiation mutation breeding.After irradiation breeding, potato, wheat, rice, cotton, soybean and other crops can have high yield, early maturity, dwarf and resistanceDiseases and pestsAnd other advantages.
2) Irradiation preservation
Irradiation preservation includes heat treatment, dehydration, cold storageChemical processingA new fresh-keeping technology developed after traditional fresh-keeping methods.For example, the irradiation treatment of potatoes, garlic, onions, etc. can inhibit their germination and extend the storage period;The supply period and shelf life of dried and fresh fruits, mushrooms, sausages, etc. can be extended by irradiation treatment.
3) Irradiation insecticidal and sterilization
At present, chemical fumigation is widely used for insecticidal sterilization of agricultural products and foodethylene oxideSuch as residual toxicity caused by chemical fumigation, destruction of atmospheric ozone layer, etcMontreal ConventionThe use of methyl bromide will be banned globally by 2005.Therefore, the use of accelerators for irradiation of agricultural products, food and other insecticides, sterilization can be rapidly developed.The high-energy electrons or X-rays generated by the accelerator can kill parasites and pathogenic bacteria in agricultural products and food, which can not only reduce the losses caused by food corruption and pests, but also improve the hygienic grade and added value of food.
medical and health work
With the progress of science and technology and the improvement of people's life and quality, people put forward higher requirements for medical and health conditions.The application of accelerator in medical and health has promoted the development of medicine and the extension of human life.At present, the application of accelerator in medical and health mainly includes three aspects, namelyRadiotherapyProduction of medical isotopes and disinfection of medical instruments, medical supplies and drugs.
1) Radiotherapy
be used forMalignant tumorRadiotherapyMedical acceleratorIt is one of the largest and most mature accelerator applications in the world today.
The accelerator used for radiotherapy has developed from an induction accelerator in the 1950s to a medical electron cyclotron in the 1960s, entering the 1970sMedical electron linear acceleratorGradually occupied the leading position.At present, there are more than 3000 medical electron linear accelerators in hospitals around the world.
In addition to the application acceleratorElectronic wireBesides X-ray radiotherapy, accelerator can also be usedProton radiotherapy, neutron radiation therapy, heavy ion radiation therapy and π meson radiation therapy. These cancer treatment methods are still in the experimental stage. The experimental results show that the efficacy is significant.However, these accelerators have much higher energy, much more complex structure and much more expensive than electron linear accelerators, and have not yet been popularized.
The use of electron linear accelerator to carry out stereotactic radiotherapy, commonly known as X-knife, is a new radiotherapy technology developed in recent years.Compared with conventional radiotherapy, this technology can protect 15%~20% more normal tissues, and increase the dose of tumor by 20%~40%, which can kill cancer cells more effectively, thus increasing the curative effect of radiotherapy.
In the 1960s, Chinese hospitals were equipped with medical induction accelerators, and in the mid-1970s, medical electron linear accelerators began to be equipped in hospitals all over China.By the beginning of 2000, China had about 530 medical accelerators of various energies, including about 230 domestic ones and about 300 imported ones.
2) Medical isotope production
Radioisotopes are widely used in modern nuclear medicine to diagnose diseases and treat tumors. Today, about 80 kinds of isotopes have been identified for clinical application, of which 2/3 are produced by accelerators. In particular, neutron deficient short-lived isotopes can only be produced by accelerators.These short-lived isotopes are mainly used in the following aspects:
PET is first inhaled or injected by the patient to emit positrons with extremely short half-lifeRadionuclideDetect the positrons emitted by these radionuclides and the photons emitted during annihilation from all angles through the annular detector, and reconstruct the sectional tissue image after computer processing.These short-lived radionuclides are prepared by small cyclotron.The shortest half-life nuclide, such as O-15, is only 123 seconds, usually a few minutes to about an hour.Therefore, this accelerator is generally equipped in hospitals using PET.The small cyclotron used to produce short-lived radionuclides for PET has attracted many accelerator manufacturers to develop and develop.At present, several foreign accelerator manufacturers have produced dozens of small cyclotrons.
b、Image acquisition
Scintillation scanning with radionuclides or image acquisition with gamma photography can be used to diagnose tumors, examine human organs, study their physiological and biochemical functions and metabolic conditions, and obtain dynamic data.For example, Tl-201 is used for myocardial examination to detect coronary heart disease andmyocardial infarctionAt present, the most sensitive inspection means are the positioning of.Most of these radionuclides are also produced by accelerators.
3) Irradiation disinfection
The sterilization and disinfection of medical devices, disposable medical items, vaccines, antibiotics and Chinese patent medicines by accelerator is a promising direction for the application of accelerator in medical health.It can replace the high-temperature disinfectionChemical disinfectionEtc.But what is needed for sterilizationRadiation doseIt should be greater than the dosage required for pest control.
